In wired communication systems, like for example wired Ethernet, data is provided to an end node unit via the data path given by a cable connecting the end node unit's network interface and a data forwarding device on the communication network. In state of the art wireless communication systems, RF signals are used for data communication between an end node unit and data forwarding device on the communication network. Although RF signals can be transmitted through walls, a sufficient number of wireless RF access points is required to guarantee that a user will obtain a proper connection to the communication network. However, a dense distribution of RF transceivers will occupy bandwidth in the spectrum, effectively limiting bandwidth available to each connected end node unit.
A new type of communication networks is emerging, where the communication is performed by light waves. Light sources may be used to transmit data to a receiver. The light waves may be visible or invisible to the human eye. A major difference to RF signalling is that light signals are line-of-sight-connections that will be obstructed by obstacles such as walls. A light source may be a lighting device normally used for ambient lighting of a space in a building, also known as Visible Light Communication (i.e. VLC). Since VLC's main objective is high quality ambient lighting, the data transmit rates are rather limited. Light sources primarily used for ambient lighting are therefore slow data transmission devices. In order to achieve higher transmission data rates data transmission light sources that are not primarily tailored at ambient lighting may be used alternatively or in addition. Examples are for instance—but not limited to—emitters using changes in light levels (on, off, dimming, colours), using multiple colours simultaneously (e.g. RGBW), a laser source or IR or UV sources. These latter examples work best with a specific receiver, such as for example an optimized photo detector.
Light emitters may be connected to a power delivering Power over Ethernet (PoE) switch using wired data ports (i.e. RJ45) as shown in FIG. 1.
An automated computer network can dynamically forward data between ports on a wired Ethernet switch using dynamical data communication path definitions. One example for implementing such dynamical data communication path definitions is a protocol such as e.g. OpenFlow or VxLan.
In order to prepare a devices used in a VLC system for data communication requires a separate protocol. With increasing network density and increasing data transfer to multiple (mobile) receivers a dynamic configuration of VLC emitters is required to offer data to the respective (mobile) receiver.
US 2011/069957 A1 discloses a method and system for light channel assignment. In order to determine an available light channel, an end-user device receives a beacon message from a light emitter to coordinate time synchronization with the light emitter and to search for an available wavelength channel. In response to the beacon message the end uses unit constructs available wavelength channel information and transmits an initial request to the light emitter. Thus, channel allocation is negotiated between the respective right emitter and the end user unit. With increasing density of the end-user devices the amount of traffic needed for negotiating a light channel will increase which limits the scalability of the system.
US 2009/026 9073 A1 discloses a similar approach in which a position estimation unit detects movement of the end-user device using photoreceivers. The light emitting device is configured to adjust the light source to be used for data transmission to the end-user device in order to avoid wasteful use of light sources which cannot reach the end-user device effectively. The light channel optimization is again dealt with in an autonomous manner at the light injection unit which complicates or limits coordination of light channel assignment in dense networks.
US 2013/0136457 A1 relates to systems for wireless light communication and is dedicated to preventing interference of optical signals in areas covered by at least two light emitting devices. In order to prevent that a data signal using an optical signal wirelessly transmitted to an end user device interferes with another signal using the same light channel in an area covered by to light emitting devices, different light channels are assigned to light emitters partly covering the same area. The light channel assignment of a respective light emitter is influenced by the channel assignment of neighboring light emitters.